获取DOMXpath结果低于HTML中的上一个结果

Question

I'm trying to sort through the HTML of an external website and, unfortunately, the site is very poorly organized. The data might look something like this:

<a class="title">Title One</a>
<a class="item">Item One</a>
<a class="item">Item Two</a>

<a class="title">Title Two</a>
<a class="item">Item One</a>
<a class="item">Item Two</a>    

And I'm working with an xpath query like this for the titles:

$titles = $x->evaluate('//a[@class="title"]');

Now, I want to list the titles with the items below them. Unfortunately, none of these elements are conveniently wrapped in a parent div, so I can't just filter through everything in the parent. So, I use a query like this for the items:

$titles = $x->evaluate('//a[@class="item"]');

Ideally, what I'd like to do is ONLY check for results below the current title element. So, if I'm looping through and hit "title one", I want to only check the "item" results that appear between title one and title two. Is there any way to do this?

Modifying the HTML is not an option here. I know this question is a little ridiculous and my explanation might be horrible, but if there's a solution, it would really help me!

Thanks everyone.

Answer 1

You can find the title elements first and then use the ->nextSibling() to move forward:

$html =<<<EOM
<a class="title">Title One</a>
<a class="item">Item One</a>
<a class="item">Item Two</a>

<a class="title">Title Two</a>
<a class="item">Item One</a>
<a class="item">Item Two</a>
EOM;

$d = new DOMDocument;
$d->loadHTML($html);
$x = new DOMXPath($d);
foreach ($x->query('//a[@class="title"]') as $node) {
    echo "Title: {$node->nodeValue}\n";
    // iterate the siblings
    while ($node = $node->nextSibling) {
       if ($node->nodeType != XML_ELEMENT_NODE) {
            continue; // skip text nodes
        }
        if ($node->getAttribute('class') != 'item') {
            // no more .item
            break;
        }
        echo "Item: {$node->nodeValue}\n";
    }
}

Output:

Title: Title One
Item: Item One
Item: Item Two
Title: Title Two
Item: Item One
Item: Item Two

Answer 2

You want to select all following siblings of the <a> element with the class="title" that are again <a> elements but with the class="item" and that have the first preceding sibling <a> element with class="title" being that exact first element you start to look from.

Eg in xpath, for example you're looking for the first title element:

//a[class="title"][1]

For that element the item elements are as followed:

//a[@class="title"][1]
    /following-sibling::a[
      @class="item" 
      and preceding-sibling::a[@class="title"][1] 
          = //a[@class="title"][1]
    ]

If you want to make use of that in code, you can do so by creating a relative expression to the title element and using DOMelement::getNodePath() :

$titles = $xp->query('//a[@class="title"]');
foreach ($titles as $title)
{
    echo $title->nodeValue, ":\n";
    $query = './following-sibling::a[@class="item" and 
              preceding-sibling::a[@class="title"][1] = ' .
              $title->getNodePath() . ']';
    foreach ($xp->query($query, $title) as $item)
    {
        echo ' * ', $item->nodeValue, "\n";
    }    
}

Output:

Title One:
 * Item One
 * Item Two
Title Two:
 * Item Three
 * Item Four